This invention relates to apparatus and methods for testing the walls and rims of containers and, more particularly, to apparatus and methods for testing metallic can body members for defects by the use of light.
The use of light to test containers and container materials has been known since at least 1908 as evidenced by U.S. Pat. No. 901,393 and many patents have been granted in the field, including U.S. Pat. Nos. 1,965,819; 2,229,451; 2,246,906; 2,318,856; 2,453,720; 2,481,863; 2,561,406; 2,563,213; 2,682,802; 2,729,136; 2,750,519; 2,872,039; 3,107,011; 3,159,279; 3,171,033; 3,327,849; 3,328,000; 3,416,659; 3,453,054; and 3,750,877.
The present invention relates to new and improved apparatus and methods of the general type disclosed in U.S. Pat. No. 3,750,877 in which metallic can body members are carried by a continuously rotating transfer wheel to a defect detection station whereat the open end or ends of a can body are brought into sealing engagement with sealing means, the exterior surfaces of the can body are flooded with light from a light source; and a light sensing device detects any light passing through the exterior surfaces of the can body to activate reject means to segregate defective can body members from satisfactory can body members.
Until the present invention, no light testing apparatus has been available which provided completely satisfactory results in terms of high speed accurate testing of both the walls and flange portions of can body members, relatively low cost construction, easy maintenance, and reliability in use with minimum down time for maintenance and repairs. A primary problem in the manufacture of can body members, such as, for example, one piece thin wall aluminum sheet metal can body members, is maintaining defect free flange portions. Small, e.g., 0.005 or larger, edge cracks in the flange portion may cause leaks in cans during completion of a can by association of end closing members with the can body members by application of relatively high forces to effect closure of the can body members. In addition, it is desirable to detect pin holes at least as small as 0.001 inch in the walls of the can body members which could cause leaks in use. In the beer industry, some beer manufacturers pasteurize the beer after a can has been filled and sealed, while other manufacturers do not pasteurize the beer. Often times the heat and pressure of the pasteurization process will reveal leaks in the finished cans by causing some of the contents to be driven through the cracks so that leaking cans may be visually observed and removed from the production line. However, if there is no pasteurization process, the leaks may not be detected at the time of manufacture and the leakage may contaminate or spoil adjacent containers or packages while in addition the product may deteriorate or spoil prior to consumption. Thus, in order to maintain high quality standards, it is imperative that all possible defects which may produce leaks be detected prior to completion of the can and filling of the can with the contents.
In addition, the testing apparatus is arranged and constructed so that damaged portions of the can body member other than the flange which cause the bottom peripheral rim surface to be other than in a flat condition will also be detected and rejected due to loss of vacuum by which the can body members are held during the transfer process.
The present invention provides for inspection of can body members with nearly 100% detection of such defects. It is contemplated that the percentage of successful detection of such defects is such that, on the average, approximately only one defective can body member in one million will not be detected and ejected by the testing apparatus. In addition, the present invention provides testing apparatus which is continuously operable at relatively high speeds up to or in excess of 1000 can body members per minute. Furthermore, the cost of manufacture of the testing apparatus has been substantially reduced as compared with apparatus of the type disclosed in U.S. Pat. No. 3,750,877 with maintenance, repair, and down time substantially improved to increase overall reliability. In addition, the present invention provides printing detection means for determining the presence or absence of a printed label on the exterior surface of the can body member.
Another feature of the present invention resides in the provision of new and improved light source means for flooding the exterior surfaces of the can body members with light in the test position without requiring the use of light reflective surfaces on the apparatus as have been used in prior art apparatus. In the present invention a relatively few florescent lamps are utilized, such as six to seven, whereas prior art apparatus has employed as many as 19 ultraviolet lamps including the extensive use of reflective apparatus surfaces in order to achieve satisfactory results. Instead of using reflective apparatus surfaces, it has been determined that by proper positioning of a relatively small number of lamps, and in particular florescent lamps with associated lamp reflectors and black anodization of surrounding metallic surfaces, exceptionally good results can be obtained.
In addition, the present invention provides uniform light intensity around the entire can body member by particular arrangement and spacing of the lamps. Other features of the present invention include supporting the can body members by vacuum applied to the outside bottom wall, internal pressurization of the can body member during testing, discharge of defective can body members only by inertial forces and gravity after release of vacuum, and removal of acceptable can body members directly from the transfer wheel to gravity discharge chute apparatus.
In general, the inventive concepts involve the use of a new and improved gravity feed system; a new and improved can body flange sealing system with pressurization of the seal and the can body during inspection; a new and improved lighting system; a new and improved mounting of a light detector device relative to a continuously rotating transfer wheel; new and improved ejection apparatus for removal of defective can body members from the transfer wheel; and new and improved transfer apparatus for removing non-defective acceptable can body members from the transfer wheel .